contacts and the degree of welding and crystal content of pumices varies from one ignimbrite to the other. Generally the ignimbrites are rich in crystals and pumice, are unwelded and contain few flow structures, with the exception of the welded Cueva Negra ignimbrite. Some ignimbrite eruptions were preceded by the formation of Plinian eruption columns that generated ash fallout, and there is evidence for pulsating flow in the ignimbrites. On the northern side of the Galán complex, ignimbrites extend up to away from the caldera and may have reached even larger distances prior to erosion, and they have thicknesses of . The ignimbrites have a total volume of about , with the Real Grande ignimbrite comprising over half of its volume. The volume of the individual ignimbrites increases the younger they are with the initial Blanco and Merihuaca ignimbrites having a volume of about . The last eruption may have generated a caldera that was later obliterated. Emission of lava flows occurred during the Toconquis phase as well, in general there was vigorous volcanic activity between the eruptions that formed the main ignimbrites. The Cueva Negra ignimbrite was emplaced after the Toconquis Group, and small lava domes and pyroclastic flows continued to be erupted until the Galán ignimbrite proper. The magmatic system shallowed during this time, resulting in composition changes of the erupted ignimbrites and a general increase of elevations in the region. Galán ignimbrite 2.08 ± 0.02 million years ago the rhyodacitic Galán ignimbrite proper was emplaced. Aside from a facies that remained inside the caldera and is minimally thick, ignimbrites extend outside of the caldera to distances of but with an average runout distance of and have thicknesses of ; closer to the caldera it has been largely eroded away and there are more complete exposures farther away from Galán. A contrary view is that the Galán ignimbrite was largely eroded only on its northern side by wind action, forming yardangs. The resurgent dome consists of Galán ignimbrite material, along with basement rocks. The "Toba Dacitica" outcrop away from the volcano was once considered part of the Galán eruption but later compositional differences were found. The Galán ignimbrite is fairly homogeneous and has a high crystal content; overall it appears that the eruption commenced and reached large dimensions fairly quickly without leaving time for an eruption column or distinct flow units to form, except in some places. Conversely,